Strophotron



July 28, 1959 INVENTOR.

STANLEY A. lOR/O STROPHOTRON Stanley A. Iorio, Long Island City, N.Y.,assignor, by mesne assignments, to Sylvania Electric Products inc,Wilmington, Del a corporation of Delaware Application September 17,1957, Serial No. 684,590

3 Claims. (Cl. 313-156) My invention is directed toward strophotronoscillators.

A strophotron is a multitransit electron tube adaptable for use in theVHF and UHF frequency ranges and is described, for example, in anarticle entitled A New Electron Tube: The strophotron by Hannes Alfevenand Dag Romell, published in the Proceedings of the IRE; page 1239, vol.42, No. 8, August 1954.

In the copending patent applications of Ralph H. Bartram, Serial No.680,761 filed August 28, 1957, Serial No. 682,457 filed September 6,1957, and Serial No. 682,458 filed September 6, 1957, there aredescribed various improved types of strophotrons.

In general, however, a strophotron comprises at least one elongatedaccelerator extending in a given direction and first and secondseparate, elongated reflectors separate from the accelerator andextending in said direction, the reflectors being so arranged withrespect to the accelerator that a plane defined as a play of symmetryextends through the accelerator and equidistantly between the tworeflectors, the plane also extending in the given direction.

The accelerator is maintained at a high positive potential relative tothe reflectors and the geometry of the accelerator and the electrodes isso arranged that a hyperbolic electric field distribution is establishedin the electron interaction region bounded by the accelerator and thereflectors.

A uniform magnetic field is established within the electron interactionregion, the magnetic field vector pointing in a direction perpendicularto the plane of symmetry.

A cathode is mounted in one of the reflectors adjacent one end of theaccelerator and a planar anode or collector maintained at a highpositive potential relative to the reflectors is positioned adjacent theother end of the accelerator. The surface of the collector isperpendicular to the plane of symmetry. A load is coupled between thetwo reflectors.

Under these conditions, electrons emitted from the cathode will migratetoward the collector along a curved path and will exhibit thecharacteristic strophotron behavior; i.e. the projection of this pathonto the plane of symmetry resembles a trochoid, while the projection ofthe path onto a second plane perpendicular to the plane of symmetry andextending in the direction of the accelerator and the reflectorsresembles a damped sinusoid having an axis defined by the intersectionof the two planes.

The frequency of the sinusoid is the oscillation frequency and an outputvoltage of this frequency appears across the load.

All of the above described strophotrons, however, have a commondisadvantage. As indicated previously, in all these strophotrons theplanar collector has its electron receiving surface perpendicular to theplane of symmetry. Since the magnetic field vector points in a directionpar allel to the surface of the collector, the resultant magnetic forceon electrons in the vicinity of the surface tends to urge theseelectrons .in directions perpendicular 2,897,393 Patented July as, 1959to the magnetic field vector but parallel to the surface. Further, theelectric field vector also points in a direction parallel to thecollector surface and the sinusoidal component of electron motion in thevicinity of the collector surface is so directed that the electrons tendto vibrate in a plane also paralell to this surface; i.e. the electronstend to approach this surface tangentially. As a consequence, certainelectrons are not collected by the collector and the strophotronfunctions ineificiently.

Accordingly, it is an object of the present invention to improve theelectron collection efiiciency of a strophotron.

Another object is to provide a new and improved strophotroncharacterized by an increased electron collection efliciency. I

Still another object is to increase the electron collection elficiencyof a strophotron by altering the position of the planar collector.

These and other objects of the present invention will either beexplained or will become apparent hereinafter.

In accordance with the principles of my invention, the collector isrotated through an angle of as compared to the conventional collectorposition, and both surfaces of the collector are parallel to theaforesaid plane of symmetry and perpendicular both to the magnetic fieldvector and to the electric field vector. Under these conditions, theelectrons in the vicinity of the collector are urged in directionsperpendicular to the collector surfaces with consequent increasedelectron collection efiiciency. Moreover, electron collection occurs atboth surfaces of the collector instead of the single surface hithertoused.

An illustrated embodiment of my invention will now be described indetail with reference to the accompanying drawings wherein:

Fig. 1 shows a strophotron in accordance with the invention; and

Figs. 2 and 3 graphically illustrate the electric field pattern in theelectron interaction region of the device of Fig. 1.

Referring now to Fig. 1, enclosed in an evacuated tube envelope (notshown), is a pair of first and second, Vertically displaced, elongatedaccelerators 1i and 12. Each accelerator has a uniform cross sectiondefining a branch of a hyperbola. Thefirst accelerator 10 forms an upperhyperbola branch having a central point 14, while the second accelerator12 forms a lower hyperbola branch having a central point 16. Thus, thetwo accelerators are disposed upon a first plane of symmetry whichextend in the same direction as the accelerators and which passesthrough central points 14 and 16.

Further provided are first and second, horizontally displaced elongatedreflectors 18 and 20 extending in the same direction as accelerators 10and 12. Each reflector has a uniform cross section defining a branch ofa hyperbola. The two reflectors are symmetrically disposed aboutopposite sides of the first plane of symmetry so as to define left andright hand hyperbola branches; the left hand branch having a centralpoint 22, the right hand branch having a central point 24-. Hence, thetwo reflec tors are disposed about a second plane of symmetryperpendicular to the first plane of symmetry and extending through thecentral points 22 and 24.

A uniform magnetic field is established within the region bounded by theaccelerators and reflectors, the magnetic field vector pointing in adirection perpendicular to the first plane of symmetry. (Means forestablishing this field are conventional and are not shown here.)

A cathode 34 is mounted in reflector 18 at a point intermediate to thecentral point 22 of this reflector and accelerator 10, the cathode beingadjacent one end of both electrodes. An anode or collector 30,maintained for convenience at the same potential as the accelerators 10and 12, is positioned adjacent the other end of both accelerators. Aload 38 is coupled between reflectors 18 and 20. a

Collector 36 is so positioned that it is substantially coincident withplane A and its surfaces are perpendicular to themagnetic field vector.

Electrons are emitted from the cathode at an extremely low velocity andenter the interaction region. Many of these electrons then drift towardthe collector along a curved path and exhibit the characteristicstrophotron behavior previously described.

However, as indicated above, the collector surfaces are perpendicular tothe magnetic field vector. 7

Further, it will be seen from a study of Fig. 2 (which is a plot of theelectric field lines in the electric interaction region remote from thecollector) and Fig. 3 (which is a plot of the electric field lines inthe interaction region adjacent the collector) that the electric fieldvector (which is represented by the electric field lines) isperpendicular to the plane of collector 36.

Since the electric and magnetic field vectors are substantially parallelin regions adjacent the collector surfaces, the magnetic field has noeffect on the electron trajectory in these regions, and the electricfield guides or compels the electrons to these surfaces.

The accelerator-reflector configuration of Fig. l is essentially thatshown in the above identified Bartram patent application Serial No.682,458 filed September 6, 1957. However, it is to be emphasized thatthe collector arrangement taught herein is applicable to all of the'strophotrons disclosed in the Bartram patent applications as well as tothe strophotron described in the IRE article previously cited.

While I have shown and pointed out my invention as applied above, itwill be apparent to those skilled in the art that many modifications canbe made within the scope and sphere of my invention as defined in theclaims which follow.

What is claimed is:

1. A strophotron comprising at least one elongated, electricallyconductive accelerator extending in a given direction; first and secondseparate, electrically conductive reflectors extending in said directionand disposed about said accelerator to define a plane of symmetryextending through said accelerator and equidistantly between saidreflectors, said plane extending in said given direction; anelectrically conductive planar collector positioned adjacent one end ofsaid accelerator, said collector being substantially coincident withsaid plane of symmetry; and means to establish a time invariant magneticfield about said reflectors, said accelerator and said collector, themagnetic field vector pointing in a direction perpendicular to saidplane of symmetry.

r a,s97,393 e 2. In combination, first, second, third and fourthseparate, elongated, electrically conductive members extending in aselected direction, each member, in cross section, defining a branch ofa hyperbola, said first and second members being designated asaccelerators and having positions at which said first and second membersrespectively define, in cross section, upper and lower hyperbolabranches, said third and fourth members being designated as reflectorsand having positions at which said third and fourth members respectivelydefine, in cross section, left hand and right hand hyperbola branches,said members defining a plane of symmetry which extends between saidaccelerators equidistantly between said reflectors, said plane extendingin said direction; and a planar collector positioned adjacent one end ofeach of said members, the surfaces of said collector being parallel tosaid plane.

3. In combination, first, second, third and fourth separate, elongated,electrically conductive members extending in a selected direction, eachmember, in cross section, defining a branch of a hyperbola, said firstand second members being designated as accelerators and having positionsat which said first and second members respectively define, in crosssection, upper and lower hyperbola branches, said third .and fourthmembers being designated as reflectors and having positions at whichsaid third and fourth members respectively define, in cross section,left hand and right hand hyperbola branches, said members defining aplane .of symmetry which extends between said accelerators equidistantlybetween said reflectors, said plane extending :in said direction; aplanar collector positioned adjacent one end of each of said members,the surface of said collector being parallel to said plane; and means tomaintain said first and second members and said collector at highpositive potentials with respect to said third and fourth members; andmeans to establish a time invariant magnetic field about said first,second, third and fourth members and said collector, the magnetic fieldvector pointing in a direction perpendicular to said plane of symmetry.

References Cited in the file of this patent UNITED STATES PATENTS2,284,733 Haeif June 2, 1942 2,414,121 Pierce Jan. 14, 1947 2,806,177Haefi Sept. 10, 1957 2,834,908 Kompfner May 13, 1958 2,844,753 QuateJuly 22, 1958 FOREIGN PATENTS 729,930 Great Britain May 11, 1955

